I'm 22 weeks pregnant and have no milk either. Fortunately in the last 1.5 weeks, we've cut DD's nursing down to less than 5 minutes a day. She used to have to nurse to sleep, but now we cuddle or I rock her in my arms. It was a difficult transition (because I felt the same way you do). Try to remember it is okay to express your feelings. Your DD is old enough to understand that nursing isn't comfortable for you anymore. I told my DD that it hurt to nurse because I had a baby in my tummy (and not that it was DD's fault.) You will stop feeling guilty when your DD happily falls asleep cuddled up next to you...and you will get that warm fuzzy feeling that you got nursing before you got pregnant. (At least that is what happened in my situation.)
mama to DD (7), DS (3.5), and another DS arriving in August!